Note: Descriptions are shown in the official language in which they were submitted.
1085699
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Background of the Invention ~ -
This invention relates to a fluid relay appara~us
and particularly to a diaphragm-type relay apparatus for
controlling one Eluid signal from another fluid signal.
In fluid control and operating systems, a relatively
small fluid control signal controlling a relatively large
fluid control or operating signal may be advantageously
employed within the system. Fluid relays may be employed
as a volume and/or pressure amplifier in which a first fluid
pilot signal controls a fluid output signal. In volume
amplifiers, a large output fluid volume may be controlled
within a given operating pressure range by a small pilot
signal. In other applications in which pressure amplification `~
is desired the low pressure pilot signal controls a high
lS pressure output signal. In both applications, either
direct or reverse acting response may be required. In -
typical pneumatic relay device, a multiple diaphragm assembly
-includes a pilot diaphragm defining a common wall between a
pilot chamber and an exhaust chamber. ~ supply diaphragm
forms an opposite wall of the exhaust chamber and a wall
of an output chamber. A supply chamber is coupled or
extended ~rom the output chamber and interconnected thereto
by a suitable spring-loaded valve assembly. A valve assembly
also interconnects the exhaust chamber to the output chamber
~2S with the exhaust valve seated on the supply valve assembly~
In operation, increasing pilot pressure functions to first ~ `
close the exhaust assembly to the output valve assembly.
-~ Further increases in pilot pressure function through the
exhaust valve assembly to open the supply valve assembly
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and connect supply pressure and flow to ~he output chamber,
and therefore to the load or output line. Pressure then
increases within the output chamber until balanced by the
pilot pressure and a stable output condition is created.
If ~he relay is connected to a dead ended load, the supply
valve closes and the exhaust valve remains closed against
the supply valve assembly to hold the pressure just equal
to the pilot pressure. Decreasing the pilot pressure
~irst causes the exhaust valve assembly to move from the
supply valve for exhausting of air until such time as the
equilibrium pressure condition is again established.
Increasing of pilot pressure rom that position would,
of course, again open the supply valve assembly and re-
establish an equivalent condition.
Although various modifications of this system
are employed, they generally include the separate exhaust ~ `
-chamber having a separate diaphragm connected to control
fluid exhaust either through the inter-related cascaded
exhaust-supply valve assem~ly or a separate valved conn-
ection in the output system. The spring forces and
interrelated fluid forces acting over the various diaphragms
in the conventional construction introduce deviations in ,
the system response. Generally,the relays have a significan~
hysterisis level in the presence of increasing and decreasing
input signals. In addition, depending upon the care and
special procedure of construction, commercially-produced
devices also may have significant deviztions from an ideal
linear characteristic. ~or example, a fluid repeater or
one to one booster relay desirably has an essentially
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straight line characteristic with a 1 1 ratio between
the input and output pressures and minimal offset, linear-
ity, and hysteresis. Such characteristics might generally
be obtained with careful construction and design, but gen-
erally require relatively complex and costly apparatus.
There is a need for a relatively simple, and
inexpensive booster fluid relay which produces a highly
accurate output with minimal offset, hysteresis and dev-
iation from linearity. `
Summary of the Present Invention
The present invention is particularly directed
to a fluid control apparatus employing a com~on diaphragm
unit responsive to the input pressure and the output
pressure, in combination with a separate exhaust means
controlled by such common diaphragm and a separate supply
valve assembly controlled by such common diaphragm. Thus,
generally in accordance with present invention, the exhaust ~;~
valve seat assembly and the supply valve seat assembly ~ -
are separately provided and mounted as a part of an output
chamber means. The single or common diaphragm unit is -~
constructed to directly control the sealing of the exhaust
valve means and to directly and separately control the
supply valve means. A relatively soft spring assembly
or other similar means biases the supply valve assembly
to the closed portion in contrast to rather stiff supply valve
spring required in a conventional design. The use of
the separate valving systems with the single diaphragm
has been found to significantly minimize the hysteresis
effect. High flow capacity and rapid speed of response
can be provided with the common diaphragm control of the
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exhaust and ~he supply.
More particularly, in one preferred and unique
embodiment of the present invention, a single diaphragm
defines a common wall between an input signal chamber and
output chamber. An exhaust orifice is formed within the
output chamber having a seating face parallel to and spaced
from the diaphragm. The supply valve assembly is mounted
within an inlet passageway terminating in the output
chamber which also has a load connecting passageway. An
operator for opening the valve assembly moves with the
diaphragm for opening of the valve assembly. In operatio~,
an increasing input signal first moves the diaphragm to
close the exhaust orifice and prevent output air from exhaus-
ting from the output chamber. ~ith the exhaust sealed,
remaining input pressure signal or force is transmitted
to the operator of the inlet or supply valve assembly to
positively open the valve mechanism and allow supply air to
flow into the output chamber. The output pressure builds
within the output chamber and in so doing tends to return the
diaphragm and close the supply valve assembly until the
output pressure equals the pilot pressure. When the bal- ~ -
anced condition is created, the supply valve assembly is -
closed. As the exhaust is sealed off, this effectively
seals the output chamber. In a highly practical pressure
system, the inlet or supply valve assembly includes a soft,
resilient ball with a soft spring forcing the ball onto a
valve seat to close the supply passageway. The spring can
be a relatively light or soft spring which is only suffi-
cient to hold the ball in a closed position with the supply
pressure removed. The supply pressure also exerts a force
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against the ball. The sealing force against the ball de-
creases with increasing output pressure due to the reduced
pressure differential across the ball. The control plunger
is acted upon by the diaphragm and is movable into engage-
ment with the ball and is operative to move the ball from
the valve seat with appropriate compressing of the soft spring. ;
In certain applications where high flow capacityis desired, a relatively large supply valve area can be
readily provided. This supply capacity must, o-f course, be
- 10 balanced by the exhaust system. However, to balance the
exhaust capacity with the output and the full flow capacity, ~;~
a single exhaust orifice would generally be so large as to
interfere with effective sealing of such orifice by the -
diaphragm. The inventor has found that a multiplicity
of exhaust ports or orifices can, however, advantageously
be employed to match exhaust flow capacity to supply and
output capacity while maintaining minimal leakage even
when large capacity is specified. Of course, leakage ~ -
i6 greater than with a single orifice. The use of a mul-
- tiplicity of orifices or a large orifice slightly decreases
the operative area of the diaphragm in the output chamber. ~ ~
With a multiple exhaust orifice device, offset between the ~`
pilot pressure and the output pressure increases and thus
the characteristic is not as optimum as in the low capacity
system.
The present invention thus provides a simple
and practical construction of a fluid apparatus and
particularly a one to one booster relay having good linearity,
minimal offset, hysteresis effect and the like while per-
mitting large flow capacity and improved system response.
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Brief ~escription_of Drawings
The drawings furnished herewith illustrate apreferred construction of the present invention in which
the above advantages and features are clearly disclosed as
well as others which will be readily understood from the
~ollowing description.
In the drawing:
Fig. 1 is a cross-sectional view through a~-one
to one booster relay constructed in accordance with the invention,
Fig. la is a fragmentary view on Line la-la of Fig. l;
Fig. 2 is a top view of the relay apparatus of Fig.
l with parts broken away and sectioned;
Fig. 3 is a diagramatical gr~phical-illustration
- of the input signal pressure versus the output pressure
for a relay s'hown in Figs. 1 and 2; and
Fig. 4 is a view similar to Fig. 2 of a further
embodiment of the present invention.
Descri~tion of the Illustrated Embodiment
Referring to the drawing and particularly to Figs.
1 and ~, the present invention is shown in a one to one
booster relay unit 1 connected to a fluid pressure pilot
signal source 2- and coupling a load 3 to a fluid pressure
operating source 4. The relay unit 1 includes an outer
housing 5 within which a single diaphragm 6 is located
- 25 with a pilot chamber 7 to one side of the diaphragm and
a combined exhaust and -output chamber 8 to the opposite
side of the diaphragm. An inlet port or passageway 9 is
provided to the pilot chamber for introducing the signal
pressure of source 2. A supply input port or passageway
10 is connected to the output chamber 8 and to the pressur-
ized supply or source 4. Sources 2 and 4 may be any suitable
or well known unit such as pneumatic source suitable for
operating of the load 3. The supply passageway 10 includes
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a check valve assembly 11 to selectively close the connection
to the output chamber 8. An operator 12 is acted ~pon by the
diaphragm 6 and positively opens the check valve assembly
11 for introducing air into the chamber 8 as the diaphragm
moves under the pilot signal pressure. An output passageway
or port 13 connects the output chamber 8 to the load unit
; 3 shown as dead-ended piston operator 14 having the piston
rod coupled to position a mechanical load such as a
damper 15. An e~haust port 16 is also provided in the
output chamber 8 and is selectively opened and closed by
the diaphragm 6 in response to the pilot or signal pressure `
in chamber 7 and in conjunction with the diaphragm actuation ~-
of the supply valve assembly 11 establishes and maintains
pressure in the output chamber 8 equal to the pilot `
pressure in chamber 7. The load 3 is therefore operated
at essentially the pilot pressure. The relay 1 permits
control of a large volume of operating air with a small
volume of signal air and, of course, isolates the two
systems. The use of the single diaphragm acting inde-
pendently but co-jointly on the separate exhaust system `
passageway and the separate supply valve assembly provides
a simple, reliable one-to-one booster relay having minimal
offset deviating from the ideal straight line character-
istic shown in Fig. 3 in ~erms of hysteresis effect and
iinearity. Further, if the load unit 3 consumes air, the
relay apparatus may readily control a large flow from a
suitable source 4 with essentially instantaneous system
response.
More particularly, in the illustrated embodiment
of the invention, the outer housing 5 is a two-piece
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housing including a bottom cup-shaped wall 17 within
which the output chamber 8 and respective supply and
output ports 10 and 13 are formed, and an inverted cup-
shaped wall 18 within which pilot chamber 7 and pilot port
9 are formed. The diaphragm 6 is any suitable flexible
diaphragm material and is shaped with the peripheral
portion located and clamped between the opposed outer
flanges of the two walls 17 and 18. The one flange is
provided with a suitable annular projection lg to form
a fluid tight Joint upon firm interconnecting of the
walls 17 and 18, shown connected by suitable clamping
clips 20.
The pilot port 9 is formed generally centrally
of the upper wall 18 and includes an outer mounting
hub portion 20a. A mounting bracket 21 is secured to
the upper wall 19 with a portion overlying the hub
portion for mounting of the relay apparatus upon a
suitable support, not shown. - -~
The pilot chamber 7 and the exhaust output
20 chamber 8 are essentially identical in diameter ~-~
and thus the pressures therein act upon identical areas
of diaphragm 6. As more fully described herei.nafter,
the output pressure in chamber 8 equals the pilot
pressure in chamber 7.
-25 The bottom wall 17 is provided with the
supply passageway or port 10 located centrally of the
chamber 8. The port 10 is connected to an insert in
the base of the chamber with a central passage 22,
the lower end of which defines a valve seat 23.
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A check ball 24 which :is formed of a suitable rubber-
like material is located within passageway 22 and is
urged into engagement with the valve seat by a coil
spring 25 acting between the backside of the ball 24
S and a sui~able outer ledge 26, shown as the inner ~ !
surface of a supply connecter 27. The spring 25
resiliently urges the ball 24 into sealing engagement
with the valve seat 23 to close the passageway 22 and
effectively disconnect the source 4 from the chamber 8.
For optimum steady state operation, a small
by-pass may be provided from the supply to the output
chamber 8. A practical construction includes a small
passageway~ 24a in the nature of scratch in the corner
of the seat 24 providing a minute flow past the seated
ball 2. The passageway 24a avoids hysteresis of the
pressure characteristics such as shown in Fig. 3.
In practical commerc;al production~ the -~
exhaust port 16 generally includes some leakage as a
result of the forming of the port seat. This leakage
tends to create an affect in the pressure characteristic.s.
This offset may be avoided by increasing the size of
leakage passageway 24a sufficiently to provide for
such exhaust leakage in addition to the hysteresis
leakage and thereby maintain the true 1 to 1 char-
; 25 acteristic shown in Fig. 3.
The spring 25 may be and preferably is a
relatively soft spring to minimize hysteresis of
the unit.
A plunger or valve operator 12 is acted upon
by the center of the diaphragm 6 in any suitable manner
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in alignment with the passageway 22 and extends through
chamber 8 and passageway 22 into operative engagement
with the valve assembly 11. The illustrated plunger 12
has a head 8 abutting the diaphragm and a relatively
narrow stem 47 which projects downwardly through the
passageway 22 into engagement with the valve ball 24.
The stem is formed with a square or suitable cross-
section so as to allow maximum supply flow aro~md the
plunger but whose edges guide the plunger. The base
wall of the output chamber 8 is provided with a
recess or has posts which serve as stops adJacent
passageway 22 to accomodate the unobstructed in~ard
movement of the head 28 as the pilot pressure in
chamber 7 increases and deflects the diaphragm 6 and
15 the plunger 12 inwardly. -~
The exhaust passageway or port 16 is formed ;
in the wall 17 projecting into the output chamber as
a nozzle-like member terminating in a reLatively flat -~
sealing face 31 in close paralleI relation to thç
20 diaphragm 6. The exhaust port 16 is generally located -~
to one side of the supply passageway 22 and may be
advantageously located to the opposite side from the
output port 13. The valve seat defined by the flat
face 31 is closely spaced to the diaphragm 6 in the
-25 unloaded or non-pressurized state. Slight movement
of the dia?hragm 6 is required to effectively open
and close the exhaust port 16.
In the operation of the illustrated embodiment
of the inven~ion, the signal or pilot pressure is applied
to the pilot chamber 7 and acts over the total exposed
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area o the diaphragm 6. Increasing pilot pressure
causes the diaphragm 6 to first move into engagement -
with the exhaust passageway seat 31 and thereby close
the exhaust port 16. This essentially seals chamber 8
and prevents escape of air from the output chamber 8
to atmosphere, other than for the leakage conditions
previously discussed. The exhaust port 16 is completely
and independently sealed prior to any effective
movement of the input or supply valve assembly 11 such
that the exhaust closure is essentially independent
o~ response of the supply valve assembly. Any further
input force is transmitted to the affixed plunger
12 which moves into engagement with the checl~ ball 24
of assembly 11 and then moves the ball from valve seat
23. The supply passageway 22 is correspondingly opened
and supply air flows into the output chamber 8 and ;
. ~ .-',: through the output port 13 and interconnecting line to
the load device 3. With a deadened load as shown, the
output pressure rapidly builds in the ou~put chamber ~
and connecting lines until the pressure equals the pilot
pressure. At this point, a balanced condition is
created across diaphragm 6 which is repositioned to
a neutral position. The valve ball 24 again moves ~
into engagement with the valve seat 23 as a result of ~ `
the balanced pressure on diaphragm 6 and the loading of
; spring 22. The ball is also held closed by the pressure
differential between the supply and output pressures
acting across the ball. The pilot and output pressures
act essentially over the same diaphragm area and produce
30 a one to one pressure ratio. The only dif~erential area ;~
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is that created by the small area of the exhaust port 16.
As this area may be made quite small~ offset pressure
is essentially and practically insignificant.
If the pilot pressure increases, the diaphragm
6 and the attached plunger 12 moves downwardly, opening
the supply valve assembly 11 until a new balance pressure
is created at which time the output pressure equals the
input or signal pressure.
When the pilot pressure is decreased, the output
force on the diaphragm moves the diaphragm away from the
exhaust valve seat 31. The valve assembly 11 remains
closed and the air exhausts from the output chamber 8
with a corresponding decrease in pressure. This continues
until a new equilibrium condition is again established,
15 at which time the diaphragm 6 again has moved into a -
sealing engagement with the exhaust valve face 31.
The output pressure is now reduced and essentially
equals the reduced pilot pressure.
The illustrated embodiment of t~e invention
develops an essentially accurate one to one relationship
between the output and pilot pressures over the normal
operating range. The use of the common diaphragm insures
that response and operating characteristics of the pilot
and output pressures are essentially the same.
The ratio of the exhaust valve area to the
diaphragm effective area is very small and maintains
a practical one to one pressure relationship. Hysteresis
in the relay response is also significantly minimized
as a result of the elimination of-all heavy or large
spring forces. ~ relatively soft sprin~ in contrast
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to the more conventional stiff supply valve spring
may be employed as the exhaust valve 16 is separate
and does not load the supply valve assembly. This
minimizes the required starting response pressure and
the resultant hysteresis characteristic associated with
the unseating o~ the exhaust valve unit. In a con~en-
tional system the pilot pressure m~s~ be lowered some
slight amount before the exhaust valve unseats and
thus inherently generates a resultant hysteresis in the
switching action. In this invention, as the pilot
pressure decreases, the diaphragm rapidly responds to
open the exhaust port. The diaphragm also provides
improved sealing capability such that a low leakage
steady-state flow and consumption occurs during system
operation. The illustrated embodiment of the invention
thus permits relatively high flow rate with the rapid
~! speed of response.
In applications requiring even higher flow
capacity, a larger supply valve area can be provided.
However, in order to maintain a balance between exhaust
and output flow capacities, the area of the exhaust
passageway must also be increased. The exhaust port
cross-section technically can, of course, be approp-
riately increased in size. ~owever, the sealing area
of the diaphragm increases by the same area and the
effective operating area decreases. There arè therefore
practical limitations on increasing of the exhaust
port diameter. The inventor has found that increased
- exhaust capacity may be provided by providing a plurality
of small exhaust ports, such as shown in the embodiment
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of Fig. 4. This second embodiment is essentially of
the same construction as that of Fig. 1 and only the
changes are described in the embodiment of Fig. 4,
three individual exhaust ports, 32, 33 and 34 are
distributed in spaced relation about the supply
passageway 12. The exhaust ports 32-34 essentially
correspond to that previously described and are shown
spaced by ninety degrees over the half of the output
chamber 8. The diaphragm 6 maintains effective sealing
with low leakage. ~he diaphragm effectively and
simultaneously seals and opens all of the ports 32-34
to provide the desired flow characteristic and particularly
increased flow capacity.
The total effective area of the diaphragm 6
within the output chamber 8 is, however, slightly
reduced by the area of the two additional ports. The
particular offset between the pilot and output pressure
is slightly more pronounced than with the single orifice
- area. Eowever, the modified construction does provi~e
an effective response with low leakage where slight offset
is acceptable.
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